Profen-types of compounds are typically defined as propionic acids (or esters) bearing at least one aromatic substituent, usually .alpha.- to the carboxylic function. These acids have an asymmetric carbon atom (the carbon atom adjacent to the carbonyl group) that typically produces a racemic mixture of these acids, i.e., a mixture of both the (+) and (-) or dextro and levo rotary forms. For example, ibuprofen (2-(4-isobutylphenyl)propionic acid), a commercially and pharmaceutically important chemical, is typically produced and sold as the racemic mixture. Other profen drugs are also produced as racemates and administered in this form. However, it is known that the physiological utility of the racemic mixtures is almost exclusively focused on one enantiomer, the other having either no effect or even diminishing the effect of the active enantiomer. Thus the S(+) form of ibuprofen is active in reducing inflammation and in providing an analgesic effect. See, for example, U.S. Pat. Nos. 4,851,444 and 4,877,620. The R(-) enantiomer is devoid of activity for these indications, although it is, in part, converted in vivo into the S(+) compound. Other profen pharmaceuticals, e.g., 2-(6-methoxy-2-naphthyl)propionic acid (Naproxen), are only prescribed as the single enantiomer.
Certain commercial applications of Profen-type compounds require enantiomeric mixtures of such compounds to have chiral purity in excess of 99%. Some examples of known methods for the chiral resolution of 2-(6-methoxy-2-naphthyl)propionic acid are described in U.S. Pat. Nos. 4,625,054 and 4,621,152 to Bernini, and 4,246,164 to Felder et al. However, the known processes for the production of these types of compounds having enriched chiral purity can be laborious, complex, or otherwise inefficient in commercial practice.
A welcome contribution to the art would be a highly efficient and economical process whereby partially enriched (i.e., chiral purity in the range of greater than 50% and less than 99%) stocks of these carboxylic acids may be further enriched to thereby produce enantiomeric mixtures of such compounds having high (preferably at least 99%) chiral purity. This invention is deemed to constitute such a contribution.